Remove DispositionChangePhase.

Remove DispositionChangePhase.

The problem with having a single observer method with a phase param is that it's cumbersome and error prone to use for most clients that just want to know when something *has* changed. I think it's appropriate then to create separate methods for each phase and have the client override the one (or both) that is relevant to them.

TBR=sky@chromium.org
BUG=none

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=281874

[Ben Goodger (Google), 2014-07-08 18:20:14]

The CQ bit was checked by ben@chromium.org

[commit-bot: I haz the power, 2014-07-08 18:22:33]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/ben@chromium.org/374933003/1

[commit-bot: I haz the power, 2014-07-08 19:57:24]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  android_dbg_triggered_tests on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/android_dbg_triggered...)
  win_chromium_x64_rel on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/win_chromium_x64_rel/...)

[commit-bot: I haz the power, 2014-07-08 23:21:41]

Change committed as 281874